We have been working on a small project trying to build a fun game but are having some issues. We basically need an oscillator that can be controlled by varying the distance between our hands and a metal plate (capacitor type of sensor), which then the signal converts into a PWM signal and is fed to a H-bridge that controls the fans. Our issue is the sensor part, oscillator and the converting into a decent PWM signal that idealy would go from 0-100% based on the capacitance. We have tried several types, relaxtion oscillator (square), 7414 schmitt trigger (square) and recently I also built a Variable pitch oscillator taken from a theremin guide, which generated a nice sine wave but only varied from the intervals 120-142kHz. We also could't figure out how to utilize it.
Is there any kind soul that have a great idea of how to make this a reality? Basically what we need is an oscillator that can be affected by just one capacitor where the interval of the capacitance (the hand) is around 20pF, this oscillation then somehow needs to be converted into a PWM signal. Our only challenge here is that we are limited to only analog components but pretty much have anything at our disposal, but mostly standard components, and also the 7414 is something we managed to get our hands on. We have tried to come up with a solution for a long time at a daily basis and are getting pretty frustrated.
Thank you in advance,